In recent years, active discussions have been conducted about SON (Self Organizing Network), which autonomously optimizes radio parameters and/or network configuration in a radio communication system such as a cellular system, in the light of operation cost (OPEX) reduction. The standardization of SON functions is also under way in 3GPP LTE (Long Term Evolution) (NPL 1).
SON has functions such as the following:                Self-Configuration;        Self-Optimization; and        Self-Healing.These are techniques for achieving respective different purposes. For example, purposes of self-optimization include: optimization of cell coverage and capacity (Coverage and Capacity Optimization (CCO)); optimization of a handover parameter (also referred to as a mobility parameter) (Mobility Robustness Optimization (MRO)); optimization of load balancing (Mobility Load Balancing (MLB)); and the like (NPL 2).        
Hereinafter, a brief description of SON operation will be given by using the MRO and CCO functions as an example in a 3GPP LTE radio communication system as shown in FIGS. 1 and 2. Note that macro radio base station (macro eNB) will be abbreviated to MeNB.
Referring to FIG. 1, in a radio communication system in which MeNBs 1, 2 and 3 exist, which manage cells 1, 2 and 3, respectively, it is assumed that the MeNBs 1 and 2 are provided by a vender A while the MeNB 3 is provided by a vender B, and that the MeNBs 1 and 2 are managed by a SON server A of the vender A while the MeNB 3 is managed by a SON server B of the vender B. In this system, the SON server A can recognize or detect what effect is caused on the cell 2 when the MRO function is executed in the cell 1. Moreover, the SON server A notifies the MeNB 2 of information about this effect, whereby the MeNB 2 can also recognize that the effect is caused by the MeNB 1 executing MRO in the cell 1. For example, when an effect that causes some problem in the cell 2 (e.g., KPI (Key Performance Indicator) degradation) is recognized or detected, the SON server A or MeNB 1 can mitigate such KPI degradation by reassessing the optimization of a handover-related parameter in the cell 1. Here, for reassessing the optimization, conceivable actions include: restoring the previous state; readjusting the optimized handover-related parameter toward the previous state; and the like. On the other hand, when KPI degradation is detected or recognized in the cell 3, the SON server B or MeNB 3 performs optimization for the cell 3 (e.g., optimization of a handover-related parameter).
Next, a heterogeneous network (HetNet) as shown in FIG. 2 is assumed. In this HetNet environment, it is assumed that MeNBs 1 and 2, which manage cells 1 and 2, respectively, are managed by a SON server A as in FIG. 1, while a pico eNB (PeNB) 4, which manages a pico cell 4, is managed by a SON server B of a vender B. In such a HetNet environment, the SON server A can recognize or detect what effect is caused on the cell 2 when the CCO function is executed and the transmit power is thus optimized in the cell 1. When an effect that causes some problem in the cell 2 (e.g., KPI degradation) is recognized or detected, the SON server A or MeNB 1 can suppress the KPI degradation in the cell 2 by reassessing the optimization of the transmit power in the cell 1, similarly to the above. On the other hand, when KPI degradation is detected or detected in the pico cell 4, the SON server B or PeNB 4 performs optimization for the pico cell 4 (e.g., optimization of transmit power).